This invention relates to a keyboard device for an electronic musical instrument, particularly to a key switch structure for use in a digital electronic musical instrument in which key on-off conditions of key switches are detected in a time division multiplex manner.
In prior art electronic musical instruments, a key switch is provided independently and separately for each of keys in the keyboard. This naturally requires a large number of key switch component parts and assembling processes, resulting in a complicated, bulky and costly keyboard construction. Particularly, mechanical type key switches using metal contacts require a large number of parts and it is difficult to make the keyboard structure compact. Further, metal contacts are frequently made of precious metals such as gold and silver for preventing deterioration but this is disadvantageous in respect of costs. Metal contacts are disadvantageous also in respect of easy occurrence of chattering.
In the prior art electronic musical instruments, a printed circuit board formed with stationary contacts is secured directly to a keyboard frame. This prior art structure of the keyboard however is disadvantageous in that the printed circuit board tends to be deformed or deflected due to change in temperature or like causes.
It is, therefore, an object of the present invention to provide a keyboard device which has eliminated the above described disadvantages of the prior art keyboards and is suitable for use in an electronic musical instrument employing digital techniques.
According to the invention, a movable contact member of a key switch is made of a single piece adapted for a common use for depression of plural keys. By employing this keyboard device, the number of required component parts is reduced and assembling of the instrument is simplified. Besides, the keyboard device according to the invention facilitates disposition of a movable contact member and prevents deformation or deflection of a printed circuit board formed with stationary contacts.